Plumbing through GPU context priority

TODO: Actually return priority from Render engine, instead of random
number.

Test: Compile and observe logcat.
Bug: 168740533
Change-Id: Id8d93e315162708a2a8afa1e87ebdf97ab53a20f
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 030073c..7f05a75 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -388,6 +388,8 @@
         return mFlinger->onTransact(code, data, reply, flags);
     }
 
+    auto getGPUContextPriority() { return mFlinger->getGPUContextPriority(); }
+
     /* ------------------------------------------------------------------------
      * Read-only access to private data to assert post-conditions.
      */